The present invention relates to an interference-eliminating membrane, test strips, kits and methods for use in detecting uric acid in a sample.
The measurement of uric acid in blood serum or other body fluids is a very useful and valuable tool for diagnosing and monitoring the course of a variety of pathological conditions. For example, when uric acid is present at an abnormally high concentration in the blood, it tends to be crystallized in the body joints, which causes a very painful inflammatory condition, known as gout. High uric acid blood levels are also known to be associated with such conditions as uremia, which is characterized by an excessive destruction of white blood cell nuclei, e.g., leukemia and pneumonia.
There are many substances, such as ascorbic acid, in blood serum and urine, which may be mistaken for uric acid in conventional assays. If a patient is mistakenly diagnosized as having a high level of uric acid, the patient may be erroneously subjected to a dangerous, expensive, uncomfortable, and unnecessary treatment. Therefore, the accurate determination of uric acid is not easily achieved but is essential.
There are some methods, such as a chemical or enzymatic method, for the determination of uric acid. Regarding the chemical methods for use in detecting uric acid, U.S. Pat. No. 4,348,208 taught that the reduction of alkaline phosphotungstate to tungsten blue may be used. Gindle E. M., Clin. Chem 1970; 16:536 disclosed the reduction formation of deep violet chelate of Cu(I)-2,2xe2x80x2-bicinchoninate (BCA). However, the chemical methods would be affected by interfering substances (such as ascorbic acid) in the samples, and thus the specificity is poor. Therefore, the enzymatic methods for detecting uric acid were gradually replaced between 1980-1990.
The enzymatic methods are characterized by the measurement of the absorbance of uric acid at a wavelength ranging from 290 to 293 nm. No absorbance of the reaction products of uricase will be detected at this wavelength. The absorbance decrease of uric acid after incubation with uricase is proportional to the initial value. Although the specificity of the enzymatic methods is relatively high, persons who conduct the detection of uric acid always have to pay more attention to maintain stability. In addition, enzymatic methods are more expensive than chemical methods. It is not convenient to store uricase as a protein. Therefore, enzymatic methods still practiced in specific places, such as hospitals or laboratories, and cannot be applied in counters or dispensaries.
U.S. Pat. No. 4,348,208 discloses that compounds containing mercapto arc added into the mixture of an alkaline phosphotungstate reagent and a sample to detect uric acid in the sample. However, the assay protocol disclosed in the patent still requires reagent preparation and mixture before the assay begins. This method is not convenient for common users.
Although it is known that phosphotungstate in an alkaline solvent can detect uric acid, the phosphotungstate, together with base, produces an acid-basic neutralization. In addition, phosphotungstate may change to specific forms of the phosphotungstate under different conditions, which cannot be used in the detection of uric acid.
Persons skilled in the art understand that a dry chemistry method, such as test strip is more convenient in performing an assay than a wet chemistry method. Furthermore a dry chemistry method is cheaper than an enzymatic method.
There is a need in the art for uric acid test strips and/or kits having high specificity and stability to conveniently detect uric acid in over the counter pharmacies or dispensaries, and allow non-professional persons, such as patients to determine uric acid levels according to the color change of the test reagent with uric acid in a sample.
It is an object of the present invention to provide an interference-eliminating membrane for use in detecting uric acid in a sample.
It is also an object of the present invention to provide a test strip for use in detecting uric acid in a sample.
It is a further object of the present invention to provide a kit for use in detecting uric acid in a sample.
Another object of the present invention is to provide a process for use in detecting uric acid in a sample.